Furnace



Oct. 9, 1934. o. s. HASKELL.

FURNACE Filed July 27, 1955 F'igJ.

| I I I I I I I I I I I I I I Fig. 5.

Inventor: Orin 5. Hdskeus u 7 Attorney.

4o bodying my Patented Oct. 9, 1934 FURNACE Orin S. Haskell, Scotla, N.Y., asdgnor to General Electric Company, a corporation of New YorkApplication July 2'1, 1933, Serial No. 682,434

8Claims.

My invention relates ticularly to furnaces for heat treating orannealing metals, and has for its object an improved fumace of this typewherein provision is made for speed, uniformity and accuracy of controlof the heating and cooling operation.

My invention has special application to furnaces such as disclosed inthe Farmer Patent No. 1,739,958 dated Dec. 17, 1929, in which theheating means is mounted in a hood which encloses the charge during theheating operation, after which the charge is removed from the hood,either by raising the hood or by lowering the charge, for the coolingoperation. The charge is furthermore enclosed in a metal shield whichremains over it during the heating operation and also during the wholeor substantial part of the cooling operation to prevent exposure of theheated charge to the outside air and resulting oxida- '20 tion.

In carrying out my invention I provide means for effecting a circulationof the gas inside the metal hood so as to provide for uniformity in theheating and cooling operations. More particularly, I provide a fanhaving radial blades mounted below the charge together with a supportfor the charge above the fan provided with a central aperture, wherebythe fan forces the gas outward radially to the side wall of the innermetal hood along which the air flows upward and returns centrallythrough the charge and the aperture in the support to the fan. I havealso provided means external to the metal hood for accelerating thecooling rate together 5 with a seal for the hood.

For a more complete understanding of my invention reference should behad to the accompanying drawing in which Fig. 1 is an elevation viewlargely in section of an electric furnace eminvention; Fig. 2 is anenlarged plan view showing the details of the support for the charge andthe fan; Fig. 3 is an enlarged fragmentary view showing the coolingmeans applied externally to'the hood, while Fig. 4 is a fragmentary viewsimilar to Fig. 3 showing a modified form of cooling means.

Referring to the drawing, while I have shown my invention in one form inconnection with a single, heat insulated supporting base 10, it will beunderstood that there may be a'plurality of these bases for supportingthe charge on which the charge may be placed as desired after which theheating hood 11 shown as being cylindrical in shape is placed over thecharge, as by suitable means such as a crane. The use of a plurality ofto furnaces, more parbases provides for the more efficient utilizationof the heating hood, for while one charge is being heated others may becooled or loaded on a base.

As shown, the base 10 is substantially horizon- 6o tal and it is builtup from spaced metallic plates 12 and 13 between which is suitableheatinsulating material 14, the plates being secured together bysuitable braces and supported in elevated relation with the floor orfoundation by means of a plurality of posts 15. Around theperiphery ofthe support 10 is' a channel 16 for containing a suitable sealing liquid'17, such as oil, water, or any molten or fluid compound which may bereplenished from a supply pipe -18. This seal is for a shield or casing20 which encloses the charge 21. The shield is made from a relativelythin sheet of metal and it is preferably cylindrical in form. It is openat the bottom and provided with a horizontal flange 22 at thebottomwhich rests on the base 10. The outer edge of the flange 22 isturned downward to form a second flange 23 extending around theperiphery of the shield and immersed in the sealing'fluid 1'1 whereby agas-tight seal is formed the base.

In this way the outside air is excluded from the interior of the shield20, in other words, from the heating chamber enclosed by the shield 20and the base, so that oxidation of the charge is m prevented.Furthermore, by means of suitable pipes 24 and 25 a suitable neutral orreducing gas, such as nitrogen or hydrogen or a mixture of the two, maybe admitted into the heating chamber to purge it of air and gases fromoil vapors from 90 work. I For the purpose of circulating the gas insidethe shield 20 a fan 26 is provided. Preferably the fan is operatedduring both the heating and cooling operations in order to expeditethese ,1 operatiohsLand also to provide for uniformity in temperature inall parts of-the charge. This fan is moimted in the bottom of theheating chamber on the base 10, preferably in such posi- ,tion on thebwerthat it is centrally 1mm with 1 respect to the shield 20. It ismounted for rotation on a shaft 2'7 which is substantially vertical andhas its axis substantially coincident with the :yertical center line ofthe shield 20. This fan is provided with a plurality of radially extending blades 28 (Fig. 2) whereby when the fan is rotated the gas inthe heating chamber is thrown outward radially with respect to the tanand thereby caused to flow radially from the fan along the bottom of theheating chamber to the I between the shield and '5 horizontal supportingplate 30 to the center of the fan where it is the bottom of, theculation.

The upward flow of the gas along the inside of the shield is produced inpart by convection due to heat applied to the side wall of the shield'asby suitable electric heating units 31 for the charge carried on theinner wall of the hood 11. Preferably these heating units are mounted onsubstantially the entire inner wall of the hood so as to apply heatuniformly to the entire outer side wall of the shield 20. The shield, itwill-be- 0bagain thrown outward along heating chamber for recirserved,is of such size as to substantially fill the heating space enclosed bythe hood, sufllcient space being provided between the side wall of theshield and the inner wall of the hood for the heating units 31.

The supporting plate 30 is somewhat smaller than the shield so as toleave a relatively narrow space a around its periphery between it andthe shield for the circulation of the gas in the shield. The supportingplate is furthermore of special construction to facilitate the efllcientcir-' culation of the gas. -As shown, it is provided with a'flat top forsupporting the charge 21, the charge being preferably arranged ormounted on the plate in an annular form so as to leave a central openingor zone32 for the downward circulation of the gas to the centralapertures 29 in the supporting plate. On its lower side the supportingplate is provided with strengthening ribs 33 and with an. annular flange34 forming a support for the plate, which flange in turn rests on acircular supporting member 36 placed just above the fan 26. This member36 is provided with a central aperture 37 which is concentric with theaxis of rotation of the fan and through which the downwardly flowing gaspasses to the fan for recirculation. The member 36 is furthermoreprovided with a plurality of radially and circumferentially extendingsupporting blades 38 around its periphery which blades rest on the base10 so as to supp rt themember 36.

The supporting blades 38 of the member 36 are preferably curved somewhatin a plane perpendicular to the axis of rotation of the fan as shown inFig. 2, the concave surfaces of the blades facing the axis of rotationof the fan. The supporting blades 38 are furthermore arranged at a sub-.

stantial angle with radial lines extending from the axis of rotation ofthe fan and through the blades. This curved shape of the blades 38 andtheir angular relation provides for maximum emciency of flow of gasdelivered by the fan.

As shown, the fan is driven by a motor 39 mounted on a bracket 40'secured to the lower side of the supporting base 10 and having its shaftconnected through a universal or flexible coupling 41 to the shaft 27 ofthe fan. The motor operatesto drive the fan in the direction withrespect to the'blades 38 indicated in- Fig. 2 by the-arrow 42. Theefficiency of the fan is furthermore improved by mounting each fan blade2841i; a considerable angle with a radial line passing through it fromthe axis of rotation of the fan, as shown in Fig. 2, this angle beingdescribed in-a direction opposi to the direction of rotation of the fan.

Preferably the fan is formed from a circular metal plate or disc 43provided with a central hub 44 which is secured to the fan shaft 27. The

hood 11.

shaft 27, a well 45 is formed around the shaft in the supporting bracket40, the top opening of the well as defined by the bracket being sealedby providing a suitable gasket between the bracket and the supportingbase 10. At the bottom of the well a suitable packing gland 46 isprovided around the shaft 27. This oil well is maintained filled withasuitable oil from a reservoir 47 which is connected to the well througha pipe 48.

Any suitable construction may be used for the As previously noted, thehood carries on its inner face a plurality of electric heating units 31.Preferably the hood is constructed of suitable electrically insulatingand heat refractory material 50, the whole being surrounded andreinforced by a suitable metallic casing 51.. A

central attachment means 52 ,is provided at the by a casing 54 whereconnections are made "with a suitable electrical supply source.

In accordance with my invention I furthermore provide means forproviding a controlled rate of cooling of the charge .after the heatinghood 11 has been removed for the cooling operation. It will beunderstood that during the cooling operation the shield 20 remains inplace to exclude the outside atmosphere from the charge. For thispurpose I provide a metallic duct or pipe 55 which encircles the shieldat its upper end and is rigidly secured thereto as by a brazed joint 56.The pipe is provided with apertures 57 in its lower side in position todirect water or other cooling fluid from the pipe against the outer,wall of the shield. When the heating hood 11 has been removed, asuitable connection is made between a source of supply of water or othercooling fluid, and the pipe 55 and the water admitted at such a rate asto give the desired cooling rate for the charge. The water flowsdownwardover the outer surface of the shield, \thus providing an effectivecooling means.

If desired the cooling pipe may be removably supported on the hood, asby lugs 58 (Fig. 4) carried by the hood, so that it can be put inposition after the heating hood has been removed.

What Iv claim as new and desire to .secure by Letters Patent of theUnited States, is:-

1. A furnace comprising bottom, top and side walls forming a closedheating chamber, heating means adjacent said .side walls, a fan providedwithwadially extending bottom wall substantially centrally thereof forrotati about a substantially vertical axis, a supporting plate for thecharge mounted above said fan and of somewhat smaller size than thechamber so as to leave a space between said side wall for thecirculation of the gas in said chamber, said supporting plate beingprovided with a substantially central aperture for the downward flow ofgas, means for rotating blades mounted on saidits periphery and said fanwhereby the gas in said chamber is forced radially outward toward theside wall of said chamber and then upward, said gas returning downwardto the fan through a central region of saidchamber and said aperture,and stationary radially extending blades around the periphery of saidfan.

,2. A furnace comprising a supporting base, a supporting plate for thecharge mounted above said base in spaced relation therewith, a fanmounted between said base and said plate for forcing the gas in saidchamber radially outward, stationary radially extending blades aroundthe periphery of said fan, a removable shield enclosing the chargeresting on said base, means providing a gas-tight seal between saidshield and said base, a heating hood enclosing said shield and restingon said base and heating means mounted on the side wall of said hood.

3. A furnace comprising a-supporting base, a supporting plate for thecharge mounted above said base in spaced relationtherewith, said platebeing provided with a central aperture, a removable shield enclosing thecharge resting on said base, means providing a gas-tight seal betweensaid shield and said base, a heating hood enclos-' ing said shield andresting on said base, heating means mounted on the side wall of saidhood, a fan mounted between said base and said plate below said aperturearranged to force the gas in said shield' radially outward to the sidewall of said shield, the gas then-flowing upward along the side wall ofthe shield and returning through a central zone and said aperture tosaid fan, and

. stationary radially extending blades around the periphery of said fan.

4. A furnace comprising a supporting base, a fan mounted centrally ofsaid base for rotation about a substantially vertical axis, radiallyextending blades on said fan arranged to produce a radial flow of gaswhen said fan is rotated, a member above said fan provided with curvedsupports forming stationary fan blades around the periphery of said-fan,said member being provided with an aperture substantially above saidfan, a supporting plate for the charge mounted ing the charge resting onsaid base and a removabove said member, said plate being provided with acentral aperture substantially above the aperture in said member, aremovable shield enclosable heating hood enclosing said shield.

5. A furnace comprising a base, a support for the charge on said base, afan mounted between said support and said base arranged to produce acirculation of gas radially along said base, a metal shield arranged tobe placed over said fan and said support and the charge mounted on saidsupport, a hood arranged to enclose said shield, heating means carriedby said hood, and means for applying a cooling medium to the exterior ofsaid shield.

6. A furnace comprising a base, a support for the charge on said base, afan mounted between said support and said base arranged to produce acirculation of gas radially along said base, a metal shield arranged tobe placed over said fan and said support and the charge mounted on saidsupport, a hood surrounding said shield, heating means carried by saidhood and a duct means mounted on the exterior of said hood provided withorifices for directing a cooling fluid over the exterior surface of saidshield.

7. A furnace comprising a base, a support for the charge on said base, afan mounted between said support and said base arranged to produce acirculation of gas radially along said base, a 05 metal shield arrangedto be placed over said fan and said support and the charge mounted on'said support, a hood arranged to enclose said shield, heating meanscarried by said hood, duct means for directing a cooling fluid'over saidhood, and means on the exterior of said hood for removably supportingsaid duct means.

8. A furnace comprising a base, a supportfor the charge on said base, aremovable metal shield enclosing said support and the charge mounted onsaid support, a fan for producing a circulation of gas in said shield, ahood enclosing said shield, heating means carried by said hood, andmeans for applying a cooling medium to the exterior of said shield.

ORIN S. HASKELL.

